Spring systems are encountered in feeder devices for forage harvesters, which in the predominant number today are equipped with two lower feeder rollers carried in bearing supports fixed in the feeder frame or casing and two upper feeder rollers working together with these. The upper feeder rollers designated in the following as pre-pressing and pressing rollers, are carried in bearing supports in the feeder casing so that their height can be altered, in order to be able to move upwards on the drawing in of harvested crop. In doing so, the spring system has the task of applying a defined roll force to the pre-pressing rollers and to the pressing rollers, so that in conjunction with the lower feeder rollers they can on the one hand compress the crop on being drawn in and on the other hand with the aid of this roll force make possible at all the drawing-in of the crop and its transport to the cylinder chopper.
Because of the increase in performance of forage harvesters required in recent years, ever higher demands are made upon their feeder equipment, which has led on the one hand to ever wider feeder devices and higher lift heights of the pre-pressing roller and of the pressing roller and to a further increase in the flow rate of the crop. These higher demands can then be fulfilled only if the roll forces exerted by the pre-pressing roller and the pressing roller on the crop are at least so great that the crop can still be compressed into a compact mat, which cannot be pulled in from the chopper cylinder. But on the other hand they must not be so great as to cause irregularities in the feeding process and blockages in the feeder device. The roll forces must increase significantly with growing layer thickness of the crop in order to obtain a uniform compactness and to compensate for the increased friction of the crop on the sidewalls of the feeder device. In the region of smaller layer thickness on the other hand, they must be kept small so that particularly in the case of the maize harvest the grains are not knocked out of the cob by too high roll forces which in the case of large chopped lengths has a particularly negative effect. Finally it is still to be pointed out that the roll forces are applied not only by the spring system, but also by the forces of reaction from the driving moment of the pre-pressing rollers and the pressing rollers, upon which the roller weights and frictional forces are dependent when raising and lowering them. The greater proportion comes, however, from the spring system, followed by the forces of reaction. The remaining quantities are practically negligible.
Numerous spring system have previously been proposed to fulfil these requirements but the closest prior art to the present invention is believed to be that described in US2003/0188521. Such a spring system is illustrated in FIGS. 1 to 3 of the accompanying drawings, in which:
FIG. 1 shows a perspective view from the front right of a feeder device with attached chopping device;
FIG. 2 shows a side view of the left side of the feeder device; and
FIG. 3 shows the pre-pressing roller in the uppermost position and the pressing roller raised by the connecting rod and pivoting crank.
Throughout this description, references to left and right are used as a matter of convenience and are determined by standing at the rear of the forage harvester and facing the forward end in the normal direction of travel. Likewise, forward and rearward are determined by normal direction of travel of the tractor or round baler. Upward or downward orientations are relative to the ground or operating surface. Horizontal or vertical planes are also relative to ground.
In FIG. 1, there is shown a feeder device 101 of a forage harvester with a chopping device 102 arranged on it in a perspective view from the front and the right, on which the spring system is implemented.
FIG. 2 shows a side view of its left side without the chopping device 102. The feeder device 101 has two upper feeder rollers, which according to the direction of flow of the crop are designated as the pre-pressing roller 103 and pressing roller. These are arranged opposite the front lower feeder roller 106, which is in bearing supports at a fixed position in the casing 105 of the feeder device 101, and the rear lower feeder roller 107 in such a way that their distance from these can be varied. For this the bearing supports 108 of the pressing roller are held in the front ends of oscillating cranks 109 of which the opposite ends are supported in bearings on pivot bolts 110 fixed in the casing 105 of the feeder device 101 so that they can pivot. On both sides on the shaft of the pressing roller, connecting rods 112 extend between the bearing supports 108 of the pressing roller and the bearing supports 113 of the pre-pressing roller 103. By means of the system of linkages formed by the cranks 109 and the connecting rods 112, the pressing and pre-pressing rollers are guided for movement relative to their respective stationary opposing rollers 107 and 106, the pressing roller being movable along an arc centred on the fixed pivot bolts 10 and the pre-pressing roller 103 being movable along an arc centred on the axis of the pressing roller.
The pressing and pre-pressing rollers are urged towards their fixed counterparts by spring systems 120, 122 and their separation varies during use to accommodate the volume of the crop flowing between them.
FIG. 3 shows the pre-pressing roller 103 raised maximally by the crop and the pressing roller 104 raised slightly.
Each spring systems 120, 122 acting to apply pressure to compress the crop comprises a spring 124, or two concentric springs 126, 128 in the case of the spring system 122, surrounding a guide rod 123, 125 which extends upwards from the bearing support of the respective roller and passes through a hole in the casing 105 of the feeder device 101. As can be seen from FIG. 3, as the pre-pressing and pressing rollers move up, the movement is opposed by the compression of the springs 124, 126 and 128 and at the same time the rods 123 and 125 protrude upwards from the casing of the feeder device 101.
This construction has certain disadvantages because the rods 123 and 125 are constantly moving up and down. As the rods are exposed, this movement presents a safety hazard and, as the rods are also in the field of view of the operator of the harvester, they provide an unnecessary distraction. Furthermore, the rods carry stops to set the minimum separation of the two pairs of rollers and when these stops come to rest against the casing 105 they make an irritating noise.